剑指offer题九

package jianzhioffer;import java.util.Scanner;/** * 一只青蛙一次可以跳上1级台阶，也可以跳上2级……它也可以跳上n级。求该青蛙跳上一个n级的台阶总共有多少种跳法。 * */public class Solution8 { //递归解法 public static int JumpFloor(int target) {       if(target <= 0 ){       return -1;       } else if(target == 1){       return 1;       } else {       return 2*JumpFloor(target -1);       } }//非递归/*public static int JumpFloor(int target) {if(target == 1)return 1;if(target ==2)return 2;int a[] = new int[target];a[0] = 1;a[1] = 2;for(int i = 2;i<target;i++){int sum =0;for(int j =0;j<i;j++){sum += a[j];}a[i] = sum+1;}return a[target -1];}*/ public static void main(String[] args) {Scanner sc = new Scanner(System.in);int target = sc.nextInt();int sum = JumpFloor(target);        System.out.println(sum);}}